javaEEday07-DQL-Select-图表

mysql-day02-DQL.sql

@@ -172,4 +172,26 @@ where name like '%张%'
   and gender = 1
   and entrydate between '2000-01-01' and '2020-01-01'
 order by update_time desc
-limit 5,5;
+limit 5,5;
+
+-- 案例2-1：根据需求，完成员工男性与女性员工的人数统计 (1 : 男性员工 , 2 : 女性员工)
+-- 函数: if(条件表达式 , true取值 , false取值)
+select gender,count(1) from tb_emp group by gender;
+
+
+select if(gender = 1,'男性员工','女性员工') as '性别'
+     ,count(1) from tb_emp group by gender;
+
+
+-- 案例2-2：根据需求，完成员工职位信息的统计
+-- 函数: case 表达式 when 值1 then 结果1 when 值2 then 结果2 else ... end
+
+select job,count(1) from tb_emp group by job;
+
+select
+    (case job when 1 then '班主任'
+              when 2 then '讲师'
+              when 3 then '教研主管'
+              when 4 then '学工主管'
+              else '无职位' end)
+     ,count(1) from tb_emp group by job;